Coordination of gut-liver bile acid signaling by FXR

项目摘要 这个应用程序的总体目标是确定肝脏和肠道在调节中的相互作用 以胆汁酸(BA)代谢为重点的饲喂状态代谢。BAS具有生理去污剂的作用 帮助消化脂肪营养，但也作为信号分子，通过以下方式深刻影响新陈代谢 激活核和膜BA受体并介导肠道FGF15/19的诱导(人 FGF19；小鼠FGF15)。过量的BA是有毒的，因此它们的水平必须严格控制，BA 核受体FXR在这一调控中起着关键作用。尽管最近取得了进展，但潜在的机制 Bas和FGF15介导的肝脏和肠道之间的相互作用，特别是调节BA水平 Cyp7a1是BA合成酶的限速酶，其在肝脏中的表达尚不清楚。我们有 初步证据表明FGF15介导的FXR的Src磷酸化在这一过程中起重要作用 相互影响。根据我们的初步数据，我们假设FXR在Tyr-67处的Src磷酸化是 在生理条件下由FGF15信号介导，Y67FXR的磷酸化是 基因选择性转录调控对降低肝脏BA水平和终止FGF15的重要作用 发信号。为了验证这一假设，我们提出了以下具体目标：1)检测Src在体内的作用 FXR的磷酸化在调节BA水平、保护正常小鼠和正常小鼠的肝胆缺陷中的作用 挑战胆汁侮辱的小鼠，通过检测FXR和Src及其磷酸化与人类的相关性 原发性胆汁淤积症患者肝脏标本中的各种形式。2)明确FXR的功能和机制 FGF15和BA激活的Src在调节BA代谢中的磷酸化和3)确定其作用 FGF15介导的FxR的磷酸化，与PPARα协同，在终止FGF15信号中起作用。 将使用多种体外和体内方法，包括遗传和病毒产生的小鼠模型和 ChIP-SEQ基因组分析，以确定FGF19治疗小鼠的全球FXR结合位点。我们的专业知识是 核受体的翻译后修饰和BA代谢的转录调控 使我们有资格解决这个重要的研究问题，即FXR翻译后磷酸化的作用 在调节BA代谢方面。我们的提案将确定FGF15的新功能和机制- 诱导FXR的磷酸化，为BA-AND提供新的潜在治疗和诊断标志 FGF15相关疾病，包括胆汁淤积性肝病。

Project Summary The overall goal of this application is to determine the interplay between the liver and intestine in the regulation of fed-state metabolism with emphasis on bile acid (BA) metabolism. BAs function as physiological detergents to aid digestion of lipid nutrients but also function as signaling molecules that profoundly impact metabolism by activating nuclear and membrane BA receptors and also by mediating induction of intestinal FGF15/19 (human FGF19; mouse FGF15). BAs in excess are toxic so that their levels must be tightly controlled and the BA nuclear receptor FXR plays a key role in this regulation. Despite recent advances, the mechanisms underlying the interplay between the liver and intestine mediated by BAs and FGF15 to regulate BA levels, in particular hepatic expression of Cyp7a1, the rate-limiting BA synthetic enzyme, are not well understood. We have preliminary evidence that FGF15-mediated phosphorylation by Src of FXR plays an important role in this interplay. Based on our preliminary data, we hypothesize that Src phosphorylation of FXR at Tyr-67 is mediated by FGF15 signaling under physiological conditions and that Y67FXR phosphorylation is important for gene-selective transcriptional regulation to reduce liver BA levels and terminate FGF15 signaling. To test this hypothesis, we propose the following Specific Aims: 1) Examine the in vivo role of Src phosphorylation of FXR in regulating BA levels, protecting against hepatobiliary defects in normal mice and in mice challenged with biliary insults, and human relevance by examining FXR and Src and their phosphorylated forms in liver samples from primary cholestasis patients. 2) Define the function and mechanisms of FXR phosphorylation by FGF15- and BA-activated Src in the regulation of BA metabolism and 3) determine the role of FGF15-mediated phosphorylation of FXR, in coordination with PPARα, in terminating FGF15 signaling. Multiple in vitro and in vivo approaches will be used, including genetic and virally generated mouse models and ChIP-seq genomic analysis to identify FXR binding sites globally in mice treated with FGF19. Our expertise on post-translational modifications of nuclear receptors and transcriptional regulation of BA metabolism uniquely qualifies us to address this important research question of the role of posttranslational phosphorylation of FXR in regulation of BA metabolism. Our proposal will determine the novel function and mechanisms of FGF15- induced phosphorylation of FXR, and provide new potential therapeutics and diagnostic markers for BA- and FGF15-related diseases, including cholestatic liver diseases.